1. Field of the Invention
The present invention relates to a machine for machining glass sheets, and more particularly a machine for grinding the edges and/or marginal areas of a glass sheet, provided with a holding device locking the glass sheet in its machining position.
2. Description of the Prior Art
Holding devices already known on machines for grinding the edges of glass sheets have a support plate on which glass sheets are clamped either with a piston that is movable in the direction of the support plate or with a suction device in the support plate.
When locking of the glass sheet is done with a movable piston, this has the drawback that the piston and frame necessary for its retention must be placed above the support plate. Therefore, these holding devices cannot be used when the free space above the support plate must remain available for other elements of the machine, as for example, in the case of grinding machines with a carriage having two degrees of freedom. In such cases, the support plate instead is equipped with low pressure suction disks, or else the plate itself constitutes a low pressure suction plate, locking to the glass sheet being worked on due to the suction effect of the low pressure applied.
In these low pressure suction holding devices, the force with which the glass sheet is held depends on the size of the suction disks or the suction plate and it is sometimes limited by the small size of the glass sheets. If the glass sheets are small, for example the triangular side panes for automobiles, the force that can be obtained by the low pressure suction does not suffice for reliable locking, and during the grinding operations there is the danger of movement of the glass sheet in relation to the support plate.